1. Field of the Invention
This invention relates generally to techniques for performing data transfer operations, and relates more particularly to a system and method for delivering data packets in an electronic interconnect.
2. Description of the Background Art
Implementing effective methods for transferring data in an electronic interconnect is a significant consideration for designers and manufacturers of contemporary electronic devices. An electronic device in an electronic interconnect may advantageously communicate with other electronic devices in the interconnect to share data, and thereby substantially increase the capabilities and versatility of individual devices in the electronic interconnect. For example, an electronic interconnect may be implemented in a home environment to enable flexible and beneficial sharing of data between various consumer electronic devices, such as personal computers, digital video disc (DVD) devices, digital set-top boxes for digital broadcasting, enhanced television sets, and audio reproduction systems.
Effectively managing data transfer operations in an interconnect of electronic devices may create substantial challenges for designers of electronic interconnects. For example, enhanced demands for increased device functionality and performance during data transfer operations may require more system processing power and require additional hardware resources across the interconnect. An increase in processing or hardware requirements may also result in a corresponding detrimental economic impact due to increased production costs and operational inefficiencies.
Interconnect size is also a factor that affects the management of data transfer operations in an electronic interconnect. Communications in an electronic interconnect typically become more complex as the number of individual devices or nodes increases. Assume that a particular device on an electronic interconnect is defined as a local device with local software elements, and other devices on the electronic interconnect are defined as remote devices with remote software elements. Accordingly, a local software module on the local device may need to transfer data to various remote software elements on remote devices across the electronic interconnect. However, successfully managing a substantial number of electronic devices across an interconnect may provide significant benefits to a system user.
Furthermore, enhanced device capability to perform various advanced data transfer operations may provide additional benefits to a system user, but may also place increased demands on the control and management of the various devices in the electronic interconnect. For example, an enhanced electronic interconnect that effectively accesses, processes, and displays digital television programming may benefit from efficient interconnect communication techniques because of the large amount and complexity of the digital data involved.
One type of data transfer that may occur in an electronic interconnect is an isochronous data transfer. Isochronous data transfers include the guaranteed handling of data that arrives in a time-based stream that is referenced to regular intervals called cycles. Isochronous data transfers are typically used for time-sensitive applications. For example, video or audio data being transmitted across an interconnect typically needs to arrive at a display device in an uninterrupted flow with appropriate timing. Because of the need for predictable and deterministic behavior when transferring isochronous data, a fixed propagation delay and knowledge of that fixed delay typically become a significant factors.
Due to growing demands on system resources and substantially increasing data magnitudes, it is apparent that developing new and effective methods for transferring data is a matter of importance for the related electronic technologies. Therefore, for all the foregoing reasons, implementing effective methods for transferring isochronous data remains a significant consideration for designers, manufacturers, and users of contemporary electronic devices.
In accordance with the present invention, a system and method are disclosed for delivering data packets in an electronic interconnect. In one embodiment of the present invention, a connection manager in a controller device preferably initially communicates with various devices on the interconnect to set-up and control a transmission of one or more isochronous data packets.
In one embodiment, a talker device preferably transmits a data packet and corresponding time stamp over a transmission path to a listener device through one or more bus bridges that each couple adjacent busses in the electronic interconnect. Each of the bus bridges typically has a finite propagation delay. In practice, the talker device preferably transmits the data packet with the time stamp to an initial bridge A in the transmission path from the talker to a listener.
A timestamp handler in bridge A preferably performs an initial packet handling procedure by creating a marker packet that is preferably transmitted along the same transmission path as the foregoing one or more data packets. Marker information in the marker packet may include any relevant information to determine the total transmission-path delay, which may then be utilized to perform a single efficient time-stamp recalculation process at a final delay element in the transmission path.
After the creation of the marker packet, bridge A preferably transmits the data packet and the marker packet to an intermediate bridge B for intermediate packet handling procedures. In response, a timestamp handler of bridge B preferably handles the marker information of the marker packet in a manner that preferably depends on whether all the busses on the interconnect are synchronized or non-synchronized.
Bridge B then transmits the data packet and marker packet to a final bridge C in the transmission path. In response, bridge C preferably performs packet handling procedures that are similar to those performed above by intermediate bridge B to update delay information in the marker packet. Bridge C then may perform a final packet handling procedure by preferably determining a total transmission-path delay value that is based on the final version of the marker information.
Finally, bridge C preferably recalculates the time stamp to produce an adjusted time stamp value by adding the total transmission-path delay value to the original time stamp. The listener device may then accurately access and utilize the data packet precisely at the moment indicated by the adjusted time stamp value, in accordance with the present invention.
The foregoing embodiment is discussed in the context of four busses that are connected by a three bridges, where the data transmission is between a single talker and a single listener. However, the present invention is contemplated for use in interconnects comprising any desired number of busses, talkers, and/or listeners that are configured in any desired manner. The present invention therefore effectively and efficiently delivers data packets in an electronic interconnect.